Trying to build qtwebkit, I get unresolved symbols for u_tolower_48 and other icu related functions, when linking JSC.
I encountered the issue on Ubuntu 12.04 after installing the current installer package including the sources, and then trying to build qtwebkit by simply using "qmake && make".
Now after taking a quick look, it seems that my system provides ICU with suffix _48.
While the ICU version that we ship within Qt is _49.
Since we do not ship the unicode headers in Qt, any project requiring ICU headers will fall back to using the headers provided by the system. But due to qmake it will link to ICU-version that comes with Qt. I assume that therefore linking would fail for any project that internally uses ICU as well.